A diver removes invasive algae from a reef off Oahu, Hawaii using a "super sucker" vacuum.Hawaii's Division of Aquatic Resources

Researchers at the Hawaii Institute of Marine Biology (HIMB) and the state’s Division of Aquatic Resources have come up with a new method to remove invasive algae that can smother coral reefs: using an underwater vacuum in conjunction with sea urchins.

Over two years, divers removed more than 40,000 pounds of invasive macroalgae blanketing six acres of coral reefs off Oahu, Hawaii using a “Super Sucker” vacuum. Researchers then introduced 99,000 young hatchery-raised sea urchins — the Hawaiian native collector urchin, Tripneustes gratilla — to feed on the remaining algae. In total, they were able to reduce the amount of algae on a reef off of Oahu by 85 percent, according to the study, published this week in the journal Peer J.

“This management approach is the first of its kind at the reef-scale,” Chris Wall, a Ph.D. candidate at HIMB, said. “Our research shows promise as an effective means to reduce invasive macroalgae with minimal environmental impact, while also incorporating a native herbivore to regulate a noxious invasive species.”

The Hawaiian researchers said their reef-cleaning technique has an ancillary benefit: the production of fertilizer. After divers suck up the nutrient-rich microalgae, it is then sorted, bagged, and delivered to farmers, who apply it to taro, sweet potato, and other crops.